CPU-D4 R11 with FECU R12 1

[Ghoulam]

Hi gurus

I have found in my office an old CPU-D4 release R11 which is the mother board of BP250.
I want to use the board but I need a FECU, and the only one I have is R12, and when I put it on the board it doesn't recognize it (the FECU is good I've tested it on a CPU-D5).
Do I have to upgrade the board to R12 or higher?
Second question: is the upgrade possible by burning software Eeproms ? because the board I have is not upgradable remotely.

Thanks to all in advance

 

[xs650]

you can upgrade the D4 by a eprom change (sw and fw) to R12.
But if it is not a hardware code 1 CPU, I would upgrade to R18 cause
then this system is supported by Aastra again.

 

[Ghoulam]

But why the R12 FECU is not recognized by R11?
It's not supported?

 

[xs650]

R11 only knows fecus till R11. This is the way the system works.
Or Siemens would say: works as designed